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Thursday, January 29, 2015

Note #1 Absolute pressure v. Gauge pressure - What on earth is NDT talking about? The effect on the pressure in a football due to a change in temperature is one of the easiest physics problems there is. The formula is PV = nrT. Solve for the change in P by dividing by V. Everything but T is constant so the change in pressure is the ratio of the new temp. to the old temp. If you fill the ball in a 90 degree room and take it to a 20 degree environment the pressure will be 22% lower in the ball. If you start with 13#'s in the ball you would end with about 10#'s in the ball.

"It doesn't happen very often, but astrophysicist Neil deGrasse Tyson was wrong this week. And like any good scientist, he's not afraid to admit it, correct it and explain himself.

"Coach Bill Belichick had said atmospheric pressures and balls being transported from the warm indoors out onto a cold field could have caused them to lose enough pressure to fall below league standards. But Tyson tweeted that to lose as much pressure as the balls did, they would need to be inflated with 125-degree air.

"He wrote that his mistake was using absolute pressures instead of gauge pressures. Going by gauge pressures, the balls would need to be inflated with 90-degree air."Note #1

"'A delightfully moot point since neither temperature absolves the NE Patriots even as we all know that the NE Patriots, in their 45 to 7 victory over the Colts, would have won the game no matter the ball pressure," he wrote. "And, as far as I am concerned, the Patriots would have won that game even in the vacuum of space.'"